During manufacture of spur and helical gears, a gear's pitch circle may become non-concentrically located with respect to the gear's axis of rotation. This can result from an accumulation of machining tolerances during manufacture, or simply, the result of wear from continued use of the gear production apparatus. Such misalignment causes, at best, "noisier" gear function and, at worst, a gear which will fail much earlier than its anticipated lifetime.
Apparatus exists to detect and plot the relationship of a gear's pitch circle to its axis, e.g., see U.S. Pat. Nos. 4,610,091 and 4,646,443 of Bertz et al. and Hoffler. In both of those patents, an automatic test apparatus is described which determines circumferential spacing of gear teeth, deviations in tooth thickness, tooth gaps, and gear concentricity. In U.S. Pat. No. 3,522,524 of Smith et al., an apparatus is described for determining the pitch of succeeding gear teeth.
These references, while enabling the concentricity of a pitch circle to a gear's axis to be determined, do not suggest what should be done if the pitch circle is found to be non-concentrically located relative to a gear's axis. Under most production circumstances, gears found not adhering to manufacturing tolerances are either scrapped or sent back for rework, if the tolerance variations are modest. In either event, significant expense is added to the cost of the gear's manufacture.
Accordingly, it is an object of this invention to provide a method and apparatus for adjusting, during manufacture, the axis of a spur or helical gear so that it is concentric with the gear's pitch circle.
It is another object of this invention to provide a gear-holding chuck which is particularly adapted to hold helical gears during pitch circle/axis adjustment.